C#LINQ问题,为什么需要新的？

Question

为什么我们需要new在select对其中一个说法？

var runs = from sampleDataTable in db.SampleData 
           from sampleInfoTable in db.SampleInfo
           where sampleDataTable.SampleInfo.SampleInfoId == sampleInfoTable.SampleInfoId
           select new {sampleDataTable.Timestamp, sampleDataTable.SampleDataId, sampleInfoTable.Lane} ;

和

var runs2 = from sampleDataTable in db.SampleData
            from sampleInfoTable in db.SampleInfo
            where sampleDataTable.SampleInfo.SampleInfoId == sampleInfoTable.SampleInfoId
               && sampleDataTable.Timestamp == timestamp
            select sampleInfoTable.Lane;

Answer 1

因为您选择的是新的匿名类型,而不是单个属性.

示例1将包含IQueryable您的匿名类型..

每个元素都将包含具有您定义的属性的类型.例如:

foreach (var result in resultset)
{
    Console.Writeline(string.Format("{0}\n{1}\n{2}\n{3}\n",
                      result.TimeStamp,
                      result.SampleDataId,
                      result.Lane));
}

Answer 2

我相信new是必需的,因为您正在创建一个包含select语句中的列和类型的新匿名类型.